Screw threads are often used as the force-producing mechanism in clamps. They are also used in various mechanisms which utilize a screw thread as a measuring device wherein the thread pitch is a distance reference. In conventional structures, a nut is engaged on the screw thread. However, in conventional mechanisms, the screw must be rotated with respect to the nut when it is desired to position the nut at a different location along the screw.
A few mechanisms have been developed where it is possible to disengage the nut from the screw in order to permit quick linear motion of the nut along the length of the screw. These have various drawbacks. When a spring is used to thrust the nut laterally against the screw, the limiting axial force on the screw is the spring force times the cosine of the thread angle. When the geometry is created to use the axial force of the screw with respect to the nut to thrust the nut into engagement with the screw, large screw bending forces are created which limit the axial force applied by the screw to a function of its columnar strength. Thus, there is need for a quick closing clamp and related structure which is capable of rapid adjustment and large forces without creating undue bending forces on the screw.